The present invention relates to silver halide photographic emulsions and silver halide photographic materials using said emulsions. More specifically, the present invention provides silver halide photographic emulsions exhibiting an excellent solution storage stability and silver halide photographic materials exhibiting low fog, excellent graininess and less residual color after rapid processing.
It is well known that sensitizing dyes used for spectral sensitization have noticeable effects on the performance of silver halide photographic materials. Trivial structural changes of sensitizing dyes often give an extreme influence on various photographic properties such as speed, fog, storage stability, residual color (i.e. , coloration after processing) or graininess. Similar phenomena are observed when two or more kinds of sensitizing dyes are used together. In both cases, it is substantially impossible to predict such influences in advance. Hence, emulsion researchers have synthesized a vast number of sensitizing dyes and studied the photographic effects of various combinations of those sensitizers for many years In spite of such efforts, the prediction of the photographic properties obtained by the use of sensitizing dyes is still almost impossible.
While photographic materials are expected to have higher speeds as well as better image quality, rapider photographic processing and reduction of processing waste for environmental protection are also urgently demanded. Therefore, technologies to achieve a high photographic speed by spectrally sensitizing silver halide grains without causing adverse effects such as fog or residual color are becoming more and more important.
Tabular grains are advantageous for spectral sensitization as the surface area per grain volume (specific surface area) is large, thus permitting the adsorption of a large amount of sensitizing dyes and improving speed/graininess ratio. On the other hand, the sensitizing dyes tend to remain in the material after processing, and the problem of residual color is serious as compared to the emulsions consisting of regular grains.
Separately, rapid processing that is eagerly expected tends to increase the amount of residual sensitizing dyes in the emulsion, thus making the problem of residual color more serious. Accordingly, techniques of reducing residual color have been earnestly expected.
It is already known that enhancement of the hydrophilic property of sensitizing dyes is effective to reduce residual color. However, the adsorption of hydrophilic dyes on silver halide grains is generally weak, causing adverse effects on the photographic properties of the resulting emulsion including speed reduction. Such a conflict has set a severe limitation on the improvement of residual color.
Moreover, a large amount of sensitizing dye adsorbed on the surface of tabular grains hinders the function of gelatin as protective colloid, leading to the sticking of grains in particular with high aspect ratios initiated by mutual contact of the main crystal plane. Such grain sticking readily proceeds to aggregation, which causes various adverse effects such as increase of fog and decrease of sensitivity as well as deterioration of graininess at solution storage of emulsion. The means for dissolving the problems is described in JP-A-6-332091 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), which discloses a method of adding a fine grain silver iodo-bromide emulsion that is substantially insoluble in water, during or after the chemical sensitization of the main emulsion. However, this method is applicable only to limited types of emulsion; in particular, it is not applicable to silver halide emulsions with high chloride contents. Thus, alternative methods applicable to the emulsions with high chloride content have been expected.
The object of the present invention is to provide silver halide photographic emulsions having an excellent solution storage stability, and silver halide photographic materials which have high sensitivity and excellent graininess showing reduced residual color ven after rapid processing.
As the result of our extensive study, the problems described above have been solved by the materials and method described in the following embodiments (1) to (14).
(1) A silver halide photographic material comprising at least one silver halide photographic emulsion layer provided on a support, wherein the emulsion layer contains at least one compound represented by formula (I) and at least one compound represented by formula (II): 
wherein Y represents an atomic group necessary to form a heterocyclic ring or an atomic group necessary to form a benzene ring condensed with a heterocyclic ring, which may further be condensed with another carbocyclic ring or another heterocyclic ring or may be substituted; Z1 and Z2 each represents an atomic group or a single bond necessary to form a nitrogen-containing heterocyclic ring which may be further condensed with another carbocyclic ring or heterocyclic ring or may be substituted; R represents an alkyl group, an aryl group or a heterocyclic ring; D represents a group necessary to form a methine dye; L1 and L2 each represents a methine group; p is an integer of 0 or 1; M represents a counter ion and m is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule: 
wherein Z31 and Z32 each represents an atomic group necessary to form anitrogen-containing heterocyclic ring which may be condensed with an aromatic or a non-aromatic carbocyclic ring and may be substituted, provided that the atomic group is not condensed with an aromatic or non-aromatic heterocyclic ring; R31 and R32 each represents an alkyl group, an aryl group or a heterocyclic ring; L31, L32, L33, L34, L35, L36 and L37 each represents a methine group; p31 and p32 each represents an integer of 0 or 1 ; n3 represents an integer of from 0, 1, 2, 3 or 4 ; M3 represents a counter ion and m3 is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule.
(2) The silver halide photographic material as described in (1), wherein Y in formula (I) represents an atomic group necessary to form a pyrrole ring, a furan ring or a thiophene ring that may be condensed with a carbocyclic ring or a heterocyclic ring and may be substituted, or an atomic group to form a benzene ring condensed with a pyrrole ring, a furan ring or a thiophene ring.
(3) The silver halide photographic material as described in (1), wherein Y in formula (I) represents an atomic group necessary to form a pyrrole ring, a furan ring or a thiophene ring that may be condensed with a carbocyclic ring or a heterocyclic ring and may be substituted.
(4) The silver halide photographic material as described in (1), wherein the formula (I) is chosen from formula (Ia): 
wherein Y11 represents an atomic group necessary to form a pyrrole ring, a furan ring, a thiophene ring, an indole ring, a benzofuran ring or a benzothiophene ring, which may be further condensed with a carbocyclic ring or a heterocyclic ring and may be substituted; X11 represents an oxygen atom, a sulfur atom, a selenium atom or NR13; R11, R12 and R13 each represents an alkyl group, an aryl group or a heterocyclic ring; Z11 represents an atomic group necessary to form a nitrogen-containing heterocyclic ring, which may be further condensed with a heterocyclic ring and may be substituted; L11, L12, L13, L14 and L15 each represents a methine group; p1 represents an integer of 0 or 1; n1 represents an integer of from 0, 1, 2, 3 or 4; M1 represents a counter ion and m1 is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule.
(5) The silver halide photographic material as described in (1), wherein the formula (I) is chosen from formula (Ib): 
wherein Y21 represents an atomic group necessary to form a pyrrole ring, a furan ring or a thiophene ring, which may be further condensed with a carbocyclic ring or a heterocyclic ring and may be substituted; X21 and X22 each represents an oxygen atom, a sulfur atom, a selenium atom or NR23; R21, R22 and R23 each represents an alkyl group, an aryl group or a heterocyclic ring; V21, V22, V23 and V24 each represents a hydrogen atom or a substituent, provided that the adjacent two substituents are not linked together to form a saturated or unsaturated condensed ring; L21, L22 and L23 each represents a methine group; n2 represents an integer of from 0, 1, 2, 3 or 4; M2 represents a counter ion and m is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule.
(6) The silver halide photographic material as described in (1) to (5), wherein the formula (II) is chosen from formula (IIa): 
wherein X41 and X42 each represents an oxygen atom, a sulfur atom, a selenium atom or NR43; V41, V42, V43, V44, V45 V46, V47, and V48 each represents a hydrogen atom or a substituent, provided that the adjacent two substituents may be linked together to form a saturated or unsaturated condensed ring; R41, R42 and R43 each represents an alkyl group, an aryl group or a heterocyclic ring; L41, L42 and L43 each represents a methine group; n4 represents an integer of from 0, 1, 2, 3 or 4; M4 represents a counter ion and m4 is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule.
(7) The silver halide photographic material as described in (1) to (5), wherein the formula (II) is chosen from formulae (III) or (IV): 
wherein X51 and X52 each represents an oxygen atom or a sulfur atom; V51, V52, V53, V54, V55 and V56 each represents a hydrogen atom or a substituent which that the adjacent two substituents are not linked together to form a saturated or unsaturated condensed ring; R51, R52 and R53 each represents an alkyl group, an aryl group or a heterocyclic ring; M5 represents a counter ion and m5 is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule: 
wherein X61 represents an oxygen atom or a sulfur atom; V61, V62, V63, V64, V65 and V66 each represents a hydrogen atom or a substituent, provided that the adjacent two substituents are not linked together to form a saturated or unsaturated condensed ring; R61 and R62 each represents an alkyl group, an aryl group or a heterocyclic ring; M6 represents a counter ion and m6 is an integer of 0 or 1 or more necessary to neutralize the charge of the molecule.
(8) The silver halide photographic material as described in (1) to (7), wherein the emulsion of the emulsion layer contains silver halide grains at least 50% of the total projected area of which is tabular grains with aspect ratio of not lower than 2.
(9) The silver halide photographic material as described in (1) to (8), wherein the emulsion layer contains an emulsion subjected to selenium sensitization.
(10) A silver halide photographic material having at least one silver halide photographic emulsion layer provided on a support, wherein the emulsion layer contains at least one compound represented by either of formulae (I), (Ia) and (Ib) shown above and the emulsion being subjected to selenium sensitization.
(11) A silver halide photographic material having at least one silver halide photographic emulsion layer provided on a support, in which the emulsion of the emulsion layer contains silver halide grains containing at least 80 mole % of silver chloride, at least 80% of the total projected area of the silver halide grains are tabular grains with an aspect ratio of not lower than 2, and the emulsion contains at least one methine dye represented by either of formulae (I), (Ia) and (Ib) described above.
(12) The silver halide photographic material as described in (1), wherein the emulsion of the emulsion layer contains silver halide grains containing at least 80 mole % of silver chloride and at least 80% of the total projected area of the silver halide grains is tabular grains with an aspect ratio of not lower than 2.
(13) The silver halide photographic material as described in (12), wherein the tabular grains contain at least 0.1 mole % of silver iodide, and has an outermost layer containing 1 to 6 mole % of silver iodide based on the total amount of silver.
(14) A method for forming an image by carrying out an image exposure and photographic processing for a silver halide photographic material having at least one silver halide emulsion layer provided on a support, wherein said silver halide photographic material is the one recited in (13) above and the total processing time of the photographic material is not longer than 75 sec.
(15) The method of forming an image as described in (14), wherein the image exposure is carried out by scanning exposure based on digital signals.
The present invention will be described in detail below.
In the present invention, the term xe2x80x9cgroupxe2x80x9d used to describe a specific part of a compound means that that part may be substituted with one or more substituents, which number is allowed to the possible largest value even if it is not substituted itself. For example, xe2x80x9calkyl groupxe2x80x9d means both of unsubstituted and substituted alkyl groups. Further, the substituents contained in a compound of the present invention mean any type of substituent in spite of presence or absence of substitution.
The substituent, V, which designates a substituent in general with no limitation, includes, for example, a halogen atom, an alkyl group [e.g., an alkyl group including cycloalkyl and bicycloalkyl groups, an alkenyl group including cycloalkenyl and bicycloalkenyl and alkynyl groups], an aryl group, a hetero atom-containing cyclic group (sometimes called heterocyclic group), a cyano group, a hydroxy group, a nitro group, a carboxyl group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclo-oxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group [including an anilino group], an ammonio group, an acylamino group, an aminocarbonylamino group, an alkoxyacrbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkyl- and arylsufonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclo-thio group, a sulfamoyl group, a sulfo group, an alkyl- and arylsulfinyl group, an alkyl- and arylsulfonyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an aryl- and heterocyclo-azo group, an imide group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a phospho group, a silyl group, a hydrazino group, an ureido group, and other ones well known in the art.
More concretely, V includes halogen atoms such as fluorine, chlorine, bromine and iodine, and alkyl groups containing straight-chain, branched-chain, and cyclic ones all of which may be unsubstituted or substituted. Concrete examples of such alkyl groups include C1-30 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, 2-chloroethyl, 2-cyanoethyl or 2-ethylhexyl, unsubstituted or substituted, C3-30 cycloalkyl groups such as cyclohexyl, cyclopentyl or 4-n-dodecylcyclohexyl, unsubstituted or substituted, C5-30 bicycloalkyl groups such as bicyclo[1.2.2]heptane-2-yl or bicyclo[2.2.2]octane-3-yl, and those containing plural ring structures such as tricyclo. The alkyl group involved in the substituents (for example, the alkyl group in an alkylthio group) to be explained hereinafter includes, in addition to those shown above, alkenyl, cycloalkeyl, bicycloalkenyl and alkynyl groups below. Alkenyl groups include straight-chain, branched-chain or cyclic ones which may be unsubstituted or substituted. More concretely, suitable alkenyl groups include unsubstituted or substituted, C2-30 alkenyl groups such as vinyl, allyl, prenyl, geranyl or oleyl, unsubstituted or substituted, C3-30 cycloalkenyl groups such as 2-cyclopentene-1-yl or 2-cyclohexene-1-yl, unsubstituted or substituted, C5-30 bicycloalkenyl groups such as bicyclo[2.2.1]hepto-2-en-1-yl or bicyclo [2.2.2]octo-2-en-4-yl, unsubstituted or substituted, C2-30 alkynyl groups such as ethynyl, propargyl or trimethylsilylethynyl, unsubstituted or substituted, C6-30 aryl groups such as phenyl, p-tolyl, naphthyl, m-chlorophenyl or o-hexadecanoylaminophenyl and heterocyclic ring groups. As the heterocyclic ring groups, preferable ones are 5- or 6-membered, unsubstituted or substituted, aromatic or non-aromatic heterocyclic compounds from which one hydrogen atom has been eliminated to form a monovalent group, and more preferable compounds are 5- or 6-membered, C3-30 aromatic heterocyclic groups such as 2-furyl, 2-thienyl, 2-pyrimidinyl or 2-benzothiazolyl. Moreover, cationic heterocyclic groups such as 1-methyl-2-pyridinium or 1-methyl-2-quinolinium.
V also means a cyano group, a hydroxyl group, a nitro group, a carboxyl group, an alkoxyl group (preferably unsubstituted or substituted C1-30 ones such as methoxy, ethoxy, isopropoxy, t-butoxy, n-octyloxy or 2-methoxyethoxy), an aryloxy grup (preferably unsubstituted or substituted C6-30 ones such as phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy or 2-tetradecanoylaminophenoxy), a silyloxy group (preferably unsubstituted or substituted C3-20 ones such as trimethylsilyloxy or t-butyldimethylsilyloxy), a heterocyclo-oxy group (preferably unsubstituted or substituted C2-30 ones such as 1-phenyltetrazole-5-oxy or 2-tetrahydropyranyloxy), an acyloxy group (preferably formyloxy, unsubstituted or substituted C2-30 alkylcarbonyloxy groups and unsubstituted or substituted C6-30 arylcarbonyloxy, such as formyloxy, actyloxy, pivaloyloxy, stearoyloxy, benzoyloxy and p-methoxyphenylcarbonyloxy), a carbamoyloxy group (preferably unsubstituted or substituted C1-30 ones such as N,N-dimethylcarbamoyloxy, N, N-diethylcarbamoyloxy, morphorinocarbonyloxy, N,N-di-n-octylaminocarbonyloxy and N-n-octylcarbamoyloxy), an alkoxycarbonyloxy group (preferably unsubstituted or substituted C2-30 ones such as methoxycarbonyloxy, ethoxylcarbonyloxy, t-butoxycarbonyloxy and n-octylcarbonyloxy), an aryloxycarbonyloxy group (preferably unsubstituted or substituted C7-30 ones such as phenoxycarbonyloxy, p-methoxyphenoxycarbonyloxy and p-n-hexadecyloxyphenoxycarbonyloxy), an amino group (preferably unsubstituted or substituted C1-30 alkylamino groups such as amino, methylamino and dimethylamino, and unsubstituted or substituted C6-30 anilino groups such as anilino, N-methylanilino and diphenylamino), an ammonio group (preferably ammonio and ammonio substituted with unsubstituted or substituted C1-30 alkyl, aryl or heterocyclic groups such as trimethylammonio, triethylammonio and diphenylmethylammonio), an acylamino group (preferably formylamino and unsubstituted or substituted C1-30 alkylcarbonylamino groups such as acetylamino, pivaloylamino and lauroylamino, and unsubstituted or substituted C6-30 ones such as benzoylamino and 3,4,5-tri-n-octyloxyphenylcarbonylamino),an aminocarbonylamino group (preferably unsubstituted or substituted C1-30 ones such as carbamoylamino, N,N-dimethylaminocarbonylamino, N,N-diethylaminocarbonylamino and morpholinocarbonylamino), an alkoxycarbonylamino group (preferably unsubstituted or substituted C2-30 ones such as methoxycarbonylamino, ethyoxycarbonylamino, t-butoxycarbonylamino, n-octadecyloxycarbonylamino and N-methylmethoxycarbonylamino), an aryloxycarbonylamino group (preferably unsubstituted or substituted C7-30 ones such as phenoxycarbonylamino, p-chlorophenoxycarbonyamino and m-(n-octyloxyphenoxycarbonylamino), a sulfamoylamino group (preferably unsubstituted or substituted C0-30 ones such as sulfamoylamino, N,N-dimethylaminosulfonylamino and N-n-octylaminosulfonylamino), an alkyl or arylsulfonylamino group (preferably unsubstituted or substituted C1-30 alkylsulfonylamino groups such as methylsulfonylamino and butylsulfonylamino, and unsubstituted or substituted C6-30 arylsulfonylamino groups such as phenylsulfonylamino, 2,3,5-trichlorophenylsulfonylamino and p-methylphenylsulfonylamino), a mercapto group, an alkylthio group (preferably unsubstituted or substituted C1-30 ones such as methylthio, ethylthio and n-hexadecylthio), an arylthio group (preferably unsubstituted or substituted C6-30 ones such as, phenylthio, p-chlorophenylthio and m-methoxyphenylthio), a heterocyclo-thio group (preferably unsubstituted or substituted C2-30 ones such as 2-benzothiazolylthio and 1-phenyltetrazole-5-ylthio), a sulfamoyl group (preferably unsubstituted or substituted C0-30 ones such as N-ethylsulfamoyl, N-(3-dodecyloxypropyl) sulfamoyl, N,N-dimethylsulfamoyl, N-acetylsulfamoyl, N-benzoylsulfamoyl and N-(Nxe2x80x2-phenylcarbamoyl)sulfamoyl), a sulfo group, alkyl- and arylsulfinyl groups (preferably unsubstituted or substituted C1-30 alkylsulfinyl or C6-30 arylsulfinyl groups such as methylsulfinyl, ethylsulfinyl, phenylsulfinyl and p-methylphenylsulfinyl), alkyl- and arylsulfonyl groups (preferably unsubstituted or substituted C1-30 alkylsulfonyl or C6-30 arylsulfonyl groups such as methylsulfonyl, ethylsulfonyl, phenyl sulfonyl and p-methylphenylsulfonyl), an acyl group (preferably formyl, unsubstituted or substituted C2-30 alkylcarbonyl and C7-30 arylcarbonyl groups, and unsubstituted or substituted C4-30 heterocyclo-carbonyl groups in which the carbonyl group is linked to a carbon atom in the ring such as acetyl, pivaloyl, 2-chloroacetyl, stearoyl, benzoyl, p-n-octyloxyphenylcarbonyl, 2-pyridylcarbonyl, and 2-furylcarbonyl, an aryloxycarbonyl group (preferably, unsubstituted or substituted C7-30 ones such as phenoxycarbonyl, o-chlorophenoxycarbonyl, m-nitrophenoxycarbonyl and p-t-butylphenoxycarbonyl), an alkoxycarbonyl group (preferably, unsubstituted or substituted C2-30 ones such as methoxycarbonyl, ethoxycarbonyl, t-butoxycarbonyl and n-octadecyloxycarbonyl), a carbamoyl group (preferably, unsubstituted or substituted C1-30 ones such as carbamoyl, N-methylcarbamoyl, N,N-dimethylcarbamoyl, N,N-di-n-octylcarbamoyl and N-(methylsulfonyl) carbamoyl), an aryl and heterocyclo-azo group (preferably, unsubstituted or substituted C6-30 arylazo or C3-30 heterocyclo-azo groups such as phenylazo, p-chlorophenylazo and 5-ethylthio-1,3,4-thiazole-2-ylazo), an imide group (preferably, N-succinimide and N-phthalimide), a phosphino group (preferably, unsubstituted or substituted C2-30 ones such as dimethylphosphino, diphenylphosphino and methylphenoxyphosphino), a phosphinyl group (preferably, unsubstituted or substituted C2-30 ones such as phosphinyl, dioctyloxyphosphinyl and diethoxyphosphinyl), a phosphinyloxy group (preferably, unsubstituted or substituted C2-30 ones such as diphenoxyphosphinyloxy and dioctyloxyphosphinyloxy), a phosphinylamino group (preferably, unsubstituted or substituted C2-30 ones such as dimethoxyphosphinylamino and dimethylaminophosphinylamino), a phospho group, a silyl group (preferably, unsubstituted or substituted C3-30 ones such as trimethylsilyl, t-butyldimethylsilyl and phenyldimethylsilyl), a hydrazino group (preferably, unsubstituted or substituted C3-30 ones such as trimethylhydrazino), and an ureido group (preferably, unsubstituted or substituted C0-30 ones such as N,N-dimethylureido).
Furthermore, two V""s may link together to form a ring such as aromatic or non-aromatic, hydrocarbon or heterocyclic ring, which may further condense with each other to form polynuclear condensed ring structures. Concrete examples of such rings include benzene, naphthalene, anthracene, quinoline, phenanthrene, fluorene, triphenylene, naphthacene, biphenyl, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, indole, benzofuran, benzothiophene, isobenzofuran, quinolizine, quinoline, isoquinoline, phthalazine, naphthyridine, quinoxaline, quinoxazoline, carbazole, phenanthridine, acridine, phenanthroline, thianthrene, chromene, xanthene, phenoxathiin, phenothiazine and phenazine.
Among the various groups represented by V, those having a hydrogen atom may be substituted with one of the groups described above by eliminating the hydrogen atom. Examples of such composite substituents include acylsulfamoyl, alkyl- and arylsulfonylcarbamoyl groups. Specific examples thereof include methylsulfonylcarbamoyl, p-methylphenylsulfonylcarbamoyl, acetylsulfamoyl and benzoylsulfamoyl.
Methine dyes represented by formula (I) of the present invention will be described in detail.
When Y is an atomic group necessary to form a heterocyclic ring, 5-membered unsaturated heterocyclic rings formed by Y include the following rings; pyrrole, pyrazole, imidazole, triazole, furan, oxazole, isoxazole, thiophene, thiazole, isothiazole, thiadiazole, selenophene, selenazole, isoselenazole, tellurophene, tellurazole and isotellurazole; 6-membered unsaturated heterocyclic rings include pyridine, pyridazine, pyrimidine, pyrazine, pyran and thiopyran. These rings may further condense with other 5- or 6-membered carbocyclic or heterocyclic rings to give an indole ring, a benzofuran ring, a benzothiophene ring or a thienothiophene ring. Moreover, the double bonds in these heterocyclic rings may be partly hydrogenated to give unsaturated heterocyclic rings such as pyrroline, pyrazoline, imidazoline, dihydrofuran, oxazoline, dihydrothiophene or thiazoline; or completely hydrogenated to give saturated heterocyclic rings such as pyrrolidine, pyrazolidine; imidazolidine, tetrahydrofuran, oxazolidine, tetrahydrothiophene or thiazolidine.
In the case where Y represents an atomic group necessary to form a benzene ring condensed with a heterocyclic ring, the ring structures formed by Y include indole, benzofuran and benzothiophene.
Preferable ring structures formed by Y include pyrrole, furan, thiophene, indole, benzofuran and benzothiophene, and more preferable ones are pyrrole, thiophene and furan.
Preferable nitrogen-containing heterocyclic rings formed by Z1 and Z2 are 5- or 6-membered ones such as oxazole, thiazole, selenazole, imidazole, 2-pyridine, 4-pyridine and 3,3-dimethyl-3H-pyrrole. These rings may be condensed with carbocyclic rings such as benzene, cyclohexene or naphthalene, or heterocyclic rings such as furan or thiophene in addition to the rings represented by Y.
More preferable nitrogen-containing heterocyclic rings formed by Z1 and Z2 are oxazole, thiazole, imidazole and 2-pyridine, among which the most preferable ones are oxazole and thiazole.
Each of the ring formed by Y and the nitrogen-containing heterocyclic ring formed by Z1 and Z2 may have substituents, which are exemplified by examples of substituents represented by V described above.
Preferable groups as the substituent V are alkyl groups, aryl groups, aromatic heterocyclic rings, alkoxy groups, alkylthio groups, cyano group and halogen atoms.
The alkyl group represented by R, which may be substituted or unsubstituted, include unsubstituted alkyl groups having 1 to 18 carbon atoms (i.e., C1-18), preferably C1-7, more preferably C1-4, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, dodecyl and octadecyl, substituted ones of C1-18, preferably C1-7, and more preferably C1-4 in which the substituent includes those represented by V such as aryl, unsaturated hydrocarbon, carboxy, sulfo, sulfato, cyano, halogen (fluorine, chlorine, bromine or iodine), hydroxy, mercapto, alkoxy, aryloxy, alkylthio, arylthio, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, carbamoyl, sulfamoyl, heterocyclic ring, alkylsulfonylcarbamoyl, acylcarbamoyl, acylsulfamoyl and alkylsulfonylsulfamoyl. These substituents may be further substituted.
The aryl group represented by R, which may be substituted or unsubstituted, includes unsubstituted aryl group having 6 to 20 carbon atoms (i.e. , C6-20), preferably C6-15, more preferably C6-10, such as phenyl and 1-naphthyl, substituted ones of C6-26, preferably C6-21, and more preferably C6-16 in which the substituent includes those represented by V such as alkyl, aryl, unsaturated hydrocarbon, carboxy, sulfo, sulfato, cyano, halogen (fluorine, chlorine, bromine or iodine), hydroxy, mercapto, alkoxy, aryloxy, alkylthio, arylthio, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, carbamoyl, sulfamoyl, heterocyclic ring, alkylsulfonylcarbamoyl, acylcarbamoyl, acylsulfamoyl and alkylsulfonylsulfamoyl. These substituents may be further substituted. A particularly preferred aryl group is phenyl.
The heterocyclic ring group represented by R, which may be substituted or unsubstituted, includes unsubstituted heterocyclic ring groups having 1 to 20 carbon atoms (i.e., C1-20), preferably C1-5, more preferably C1-10, such as pyrrole, furan and thiophene, or substituted ones of C1-26, preferably C1-21 and more preferably C1-16 in which the substituents are those represented by V.
Preferably, R represents a structure substituted with a group having an acid moiety or a dissociable proton such as carboxyl, sulfo, phosphonic acid, boric acid, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 and xe2x80x94SO2NHCOxe2x80x94. More preferable examples include alkyl groups substituted with either of a carboxyl group, a sulfo group, an alkylsulfonylcarbamoyl group (for example, methanesulfonylcarbonyl), an acylcarbamoyl group (for example, acetylcarbamoyl), an acylsulfamoyl group (for example, acetylsulfamoyl) or an alkylsulfonylsulfamoyl group (for example, methanesulfonylsulfamoyl). Most preferable examples are carboxymethyl, 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl and methanesulfonylcarbamoylmethyl groups.
The methine group represented by L1 and L2 may have substituents such as those represented by V described above.
The preferable value for p is 0.
M in formula (I) is included in the formula in order to indicate the presence of a cationic or an anionic ion necessary to neutralize the ionic charge of the dye molecule. Whether a certain dye is of cationic or anionic ion or has a net ionic charge depends on the substituent of the dye or the surrounding condition such as the pH of the solution Typical cationic ions include inorganic ones such as hydrogen ion (H+), alkali metal ions (Na+, K+ or Li+) and alkaline earth metal ions (Ca++) organic ones such as ammonium ion (NH4+, tetraalkylammonium ion, triethylammonium ion, pyridinium ion, ethylpyridinium ion or 1,8-diazabicyclo[5.4.0]-7-undecenium ion). The anionic ion may be inorganic or organic, including halogenated ions such as fluoride ion, chloride ion, bromide ion or iodide ion, substituted arylsulfonate ion such as p-toluenesulfonate ion or p-chlorobenzenesulfonate ion, aryldisulfonate ion such as 1,3-benzenesulfonate ion, 1,5-nahthalenedisulfonic acid ion or 2,6-naphthalenedisulfonic acid ion, alkylsulfonate ion such as methylsulfonate ion, sulfuric acid ion, thiocyanate ion, perchlorate ion, tetrafluoroborate ion, picric acid ion, acetate ion and trifluoromethanesulfonate ion. Further, ionic polymers or other dyes charged in the polarity opposite to that of the dye (i.e., other dyes having a reverse charge) may be used.
Preferable cationic ions include Na+, K+, triethylammonium ion, tetraethylammonium ion, pyridinium ion, ethylpyridinium ion and metylpyridinium ion. Preferable anionic ions include perchlorate ion, the iodide ion or bromide ion and substituted arylsulfonate ion such as p-toluenesulfonate ion.
m represents an integer of 0, or 1 or more necessary to neutralize the charge of the dye molecule, thus in the case where internal salts are formed, m is equal to 0. A preferable range of m is from 0 to 4.
D represents a group necessary to form a methine dye, and any type of methine dye may be formed by selecting a proper D. Preferable examples thereof include cyanine, merocyanine, rhodacyanine, trinuclear and tetranuclear merocyanines, allopolar, hemicyanine and styryl dyes. Detailed descriptions on these dyes are found in F. M. Hamer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Cyanine Dyes and Related Compoundsxe2x80x9d, published by John Wiley and Sons (New York, London, 1964) and p. 482 to 515, Section 14 of Chapter 18 of D. M. Sturmer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Special Topics in Heterocyclic Chemistryxe2x80x9d published by John Wiley and Sons (New York, London, 1977).
Formulae for preferable dyes include those described in the 32nd to 36th columns of U.S. Pat. No. 5,994,051, and in the 30th to 34th columns of U.S. Pat. No. 5,747,236. And, formulae for preferable cyanine, merocyanine and rhodacyanine dyes are shown as (XI), (XII) and (XIII) described in the 21st to 22nd columns of U.S. Pat. No. 5,340,694. (Note, however, n12, n15, n17 and n18, which are not limited, represents an integer of 0 or 1 or more, (preferably from 0 to 4). Preferable types are cyanine, merocyanine and rhodacyanine, among which cyanine dyes are particularly preferred.
In cases where a cyanine dye is formed by D in formula (I), the molecular structure can also be represented by resonance formula (Ixe2x80x2). 
Concrete examples of preferable compounds represented by formula (I) will be described below. The compound represented by formula (I) preferably is chosen from formulae (a) to (l). 
In the formulae, m is the same as in formula (I), X1 represents an oxygen atom, a sulfur atom, a selenium atom or NR1 in which R1 is an alkyl or aryl group or a heterocyclic ring, and X2 an oxygen atom, a sulfur atom or an NR2 in which R2 is an alkyl or an aryl group or a heterocyclic ring. The benzene and the heterocyclic rings may be substituted with any group represented by V described above, or condensed with other carbocyclic or heterocyclic ring.
Among those formulae, preferable ones are from (a) to (i), more preferable ones being from (a) to (c), and particularly preferable ones are from (a) to (c).
Most preferable cases are when the methine dyes represented by formula (I) are chosen from formulae (XI), (XII), (XIII) and (XIV). 
In formula (XI), Y, R, Z1, Z2, L1, L2 and p have the same meanings as in formula (I), and L71, L72, L73, L74 and L75 each represents a methine group. p7 represents 0 or 1. n7 represents an integer of 0, 1, 2, 3 or 4. Y71 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring which may be condensed with other carbocyclic or heterocyclic rings. M7 represents a counter ion, and m7 represents an integer of 0, 1, 2, 3 or 4 necessary to neutralize the molecular charge. R7 represents a substituted or unsubstituted alkyl, aryl or heterocyclic ring group. 
In formula (XII), Y, R, Z1, Z2, L1, L2 and p have the same meanings as in formula (I), and L81 and L82 each represents a methine group. n8 represents an integer of 0, 1, 2, 3 or 4. Y81 represents an atomic group necessary to form an acid nucleus which may be condensed with other carbocyclic or heterocyclic rings. M8 represents a counter ion, and m8 represents an integer of 0, 1, 2, 3 or 4 necessary to neutralize the molecular charge. 
In formula (XIII), Y, R, Z1, Z2, L1, L2 and p have the same meanings as in formula (I), and L91, L92, L93, L94, L95, L96 and L97 each represents a methine group. p9 represents 0 or 1. n91 and n92 each represents an integer of 0, 1, 2, 3 or 4. Y91 and Y92 each represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring which may have substituents. But, Y92 may be condensed with other carbocyclic or heterocyclic rings. M9 represents a counter ion, and m9 represents an integer of 0, 1, 2, 3 or 4 necessary to neutralize the molecular charge. R91 and R92 each represents a substituted or unsubstituted alkyl, aryl or heterocyclic ring group. 
In formula (XIV), Y, R, Z1, Z2, L1, L2 and p have the same meaning as in formula (I), and L101, L102, L103, L104, L105, L106 and L107 each represents a methine group. p10 represents 0 or 1. n101 and n102 represents an integer of 0, 1, 2, 3 or 4. Y101 and Y102 represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring which may be substituted. But, Y102 may be condensed with other carbocyclic or heterocyclic rings. M10 represents a counter ion, and m10 represents an integer of 0, 1, 2, 3 or 4 necessary to neutralize the molecular charge. R101 and R102 each represents a substituted or unsubstituted alkyl, aryl or heterocyclic ring group.
The 5- or 6-membered heterocyclic ring represented by Y71 Y92 and Y102 in formulae (XI), (XII), (XIII) and (XIV) may further be condensed with other 5- or 6-membered carbocyclic or heterocyclic rings. Such carbocyclic ring includes benzene or naphthalene ring, and such heterocyclic ring includes furan and thiophene. Preferably, the condensed ring is carbocyclic, and more preferably a benzene ring. Contretely, the 5- or 6-membered nitrogen-containing heterocyclic rings (systems) to be exemplified as the examples for Z11 in formula (Ia) are preferred, and concrete examples include the examples for Z11 Z12, Z13, Z14 and Z16 described in the 23rd to 24th columns of U.S. Pat. No. 5,340,694.
Y81 represents an atomic group necessary to form a cyclic or non-cyclic acid nucleus, and may take any type of the acid nucleus for an ordinary merocyanine dye. In preferable structures, the group adjacent to the methine chain linkage in Y81 is a thiocarbonyl or carbonyl group.
The definition of the term xe2x80x9cacid nucleusxe2x80x9d is found in p. 198 of T. H. James, xe2x80x9cThe Theory of the Photographic Processxe2x80x9d, 4th Edition, published by MacMillan Publishing Co., in 1977. Concretely, those compounds described in U.S. Pat. No. 3,567,719, No. 3,575,869, No. 3,804,634, No. 3,837,862, No. 4,002,480 and No. 4,925,777 and JP-A-3-167546.
The acid nucleus is preferably form a 5- or 6-membered nitrogen-containing heterocyclic ring comprising carbon, nitrogen and chalcogen atoms (typically, oxygen, sulfur, selenium or tellurium). Examples of preferable nucleus are listed below.
The nuclei of the following compounds; 2-pyrazoline-5-one, pyrazolidine-3,5-dione. imidazoline-5-one, hydantoin, 2- or 4-thiohydantoin, 2-iminooxazolidine-4-one, 2-oxazoline-5-one, 2-thiooxazoline-2,4-dione, isooxazoline-5-one, 2-thiazoline-4-one, thiazolidine-4-one, thiazolidine-2,4-dione, rhodanine, thiazolidine-2,4-dithione, isorhodanine, indane-1,3-dione, thiophene-3-one, thiophene-3-one-1,1-dioxide, indoline-2-one, indoline-3-one, 2-oxoindazolinium, 3-oxoindazolinium, 5,7-dioxo-6,7-dihydrothiazolo[3,2-a]pyrimidine, cyclohexane-1,3-dione, 3,4-dihydroisoquinoline-4-one, 1,3-dioxane-4,6-dione, barbituric acid, 2-thiobarbituric acid, curomane-2,4-dione, indazoline-2-one, pyrido[1,2-a]pyrimidine-1,3-dione, pyrazolo[1,5-b]quinazolone, pyrazolo[1,5-a]benzimidazole, pyrazolopyridone, 1,2,3,4-tetrahydroquinoline-2,4-dione, 3-oxo-2,3-dihydrobenzo [d] thiphene-1,1-dioxide, 3-dicyanomethylene-2,3-dihydrobenzo[d]thiophene-1,1-dioxide. And, those in which the carbonyl or thiocarbonyl group in each nucleus described above is substituted with an active methylene compound having a ketomethylene or cyanomethylene structure, linking at its active methylene site are also included.
Preferable examples of Y81 include hydantoin, 2- or 4-thiohydantoin, 2-oxazoline-5-one, 2-thiooxazoline-2,4-dione, thiazolidine-2,4-dione, rhodanine, thiazolidine-2,4-dithione, barbituric acid and 2-thiobarbituric acid, and more preferable ones are hydantoin, 2- or 4-thiohydantoin, 2-oxazoline-5-one, rhodanine, barbituric acid and 2-thiobarbituric acid. Most preferable compounds are 2- or 4-thiohydantoin, 2-oxazoline-5-one, rhodanine and barbituric acid.
The 5- or 6-membered nitrogen-containing heterocyclic ring formed by Y91 and Y101 is from the heterocyclic ring represented by Y81 from which the oxo or thioxo group has been eliminated. Preferable examples of Y81 include those obtained by eliminating the oxo or thioxyo group from hydantoin, 2- or 4-thiohydantoin, 2-oxazoline-5-one, 2-thiooxazoline-2,4-dione, thiazolidine-2,4-dione, rhodanine, thiazolidine-2,4-dithione, barbituric acid or 2-thiobarbituric acid. More preferable examples include those obtained by eliminating the oxo or thioxyo group from hydantoin, 2- or 4-thiohydantoin, 2-oxazoline-5-one, rhodanine, barbituric acid or 2-thiobarbituric acid. Particularly preferred ones are those obtained by eliminating the oxo or thioxyo group from 2- or 4-thiohydantoin, 2-oxazoline-5-one or rhodanine.
R71, R91, R92, R101 and R102 and the substituent, which is named R81 if it exists, on the nitrogen atom of acid nucleus Y81 each represents a substituted or unsubstituted alkyl, aryl or heterocyclic ring group, and preferably represents the groups exemplified as R of the methine dye represented by formula (I).
Among such groups, substituted or unsubstituted alkyl groups are preferred as R71, R81, R91, R92, R101 and R102, and more preferable ones contain an alkyl group having an acid group or a group with a dissociable proton. Most preferable ones are substituted alkyl groups containing any one of carboxyl group, sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHS2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferably ones are carboxylmethyl, 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl and methanesulfonylcarbamoylmethyl groups.
L71, L72, L73, L74, L75, L81, L82, L91, L92, L93, L94, L95, L96, L97, L101, L102, L103, L104, L105, L106 and L107 each represents a methine group independently of each other. These methine groups may have substituents, which are preferably those represented by V described above.
The methine group may form a ring together with other methine groups or with Y71, Y81, Y91, Y92, Y101 or Y102.
L1, L2, L74, L75, L96, L97, L106 and L107 preferably are unsubstituted methine groups.
n7, n8, n91, n92, n101 and n102 represent an integer of f 0, 1, 2, 3 or 4; in the case of 2 or larger, methine groups are repeated, but they need not be the same. The preferable value for n7, n8, n91 and n102 is 0, 1, 2 or 3, a more preferable range is 0, 1 or 2, and the particularly preferable value is 0 or 1. n92 and n101 each is preferably 0 or 1, more preferably 0.
p7, p9 and p10 each independently represents 0 or 1, and preferably 0.
M7, M8, M9 and M10 each represents a counter ion, and is preferably the same as M described above. m7, m8, m9 and m10 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m is equal to 0. A preferable range of m is from 0 to 4.
Among the methine dyes represented by formula (I) and further by formula (XI), (XII), (XIII) or (XIV), particularly preferable ones are those represented by formula (XI), in which those represented by formula (Ia) are more preferable.
In the following, dyes represented by formula (Ia) will be described in detail.
In formula (Ia), Y11 represents an atomic group necessary to form a pyrrole ring, a furan ring or a thiophene ring and further an indole ring, a benzofuran ring or a benzothiophene ring. The resulting compounds may further be condensed with other carbocyclic or heterocyclic rings and have substituents, but it is desirable that no other condensed ring exists. Particularly preferably rings formed with Y11 are pyrrole, furan or thiophene.
X11 which represents an oxygen atom, a sulfur atom, a selenium atom or NR13 is preferably oxygen, sulfur or NR13. In particular, oxygen or sulfur is preferred.
The nitrogen-containing heterocyclic ring formed by Z11 may be condensed with a carbocyclic ring such as benzene, cyclohexene or naphthalene or with a heterocyclic ring such as furan or thiophene, however the ring to be condensed preferably is carbocyclic, and more preferably a benzene ring.
The nitrogen-containing heterocyclic ring formed by Z11 is preferably thiazoline, thiazole, benzothiazole, oxazoline, oxasole, benzoxazole, selenazoline, selenazole, benzoselenazole, tellurazoline, tellurazole, benzotellurazole, 3,3-dialkylindolenine such as 3,3-dimethylindolenine, imidazoline, imidazole, benzimidazole, isooxazole, isothiazole, pyrazole, 2-pyridine, 4-pyridine, 2-quinoline, 4-quinoline, 1-isoquinoline, 3-isoquinoline, imidazo[4,5-b]quinoxaline, oxadiazole, thiadiazole, tetrazole, pyrimidine and those obtained by the condensation of a benzene ring to the rings described heretofore.
More preferably, the nitrogen-containing heterocyclic ring is benzoxazole, benzothiazole, benzimidazole or quinoline, and most preferably benzoxazole or benzothiazole, which may be substituted with a substituent represented by V described above. Concrete examples are those described as examples for Z11, Z12, Z13, Z14 and Z16 shown in the 23rd to 24th columns of U.S. Pat. No. 5,340,694.
As the alkyl, aryl or heterocyclic ring group represented by R11, R12 and R13, those described as R of the methine dyes represented by formula (I) can be exemplified. R11 and R12 preferably are an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl or sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups.
Preferable R13 is an unsubstituted alkyl group, and particularly preferably methyl and ethyl.
The methine groups represented by L11, L12, L13, L14 and L15 may be unsubstituted or substituted with the groups represented by V described above.
Preferably, L14 and L15 are both unsubstituted methine groups.
n1 represents an integer of 0, 1, 2, 3 or 4; in the case of 2 or larger, methine groups are repeated, but they need not be the same. Preferable values of n1 are 0, 1, 2 or 3, and most preferably 0, 1 or 2, but a particularly preferable value is 0 or 1.
p1, which is 0 or 1, and preferably 0.
M1 is substantially equivalent to M of the methine dyes represented by formula (I), and preferably a cationic ion. Preferable cations include Na+, K+, triethylammonium, pyridinium and N-ethylpyridinium.
m1 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m1 is 0. A preferred range of m1 is from 0 to 3.
The methine dyes represented by formula (Ia) preferably are further represented by formula (Ib).
Descriptions on the dyes represented by formula (Ib) will be described below.
The ring formed by Y21 in formula (Ib) is chosen from pyrrole, furan or thiophene ring.
The direction of condensation of ring formed by Y21 is arbitrary; as an example, the cases of thiophene are explained. Among the thieno[3,2-d]azole form in which the sulfur atom in the thiophene ring stands in the same side as X21 relative to the condensed carbon-carbon bond (corresponding to formula (c) of formula (I), the thieno[2,3-d]azole form in which the sulfur atom in the thiophene ring stands in the opposite side as X21 relative to the condensed carbon-carbon bond (corresponding to formula (a) in formula (I)), the thieno[3,4-d]azole form which condenses at the 3- and 4-sites of the thiophene ring (corresponding to formula (b) in formula (I)), the former two are preferred. In cases where a spectral absorption at longer wavelength regions are required as sensitizing dyes, the form represented by formula (a) is particularly suited.
Further, the ring formed by Y21 is preferably substituted with any one of substituents represented by V. Preferable substituents include alkyl groups such as methyl, aryl groups such as phenyl, aromatic heterocyclic rings such as 1-pyrrolyl, alkoxy groups such as methoxy, alkylthio groups such as methylthio, cyano group and halogen atoms such as F, Cl, Br or I. Among them, halogenatoms, in particular, chlorine or bromine atom is preferred.
X21 and X22 each represents an oxygen atom, a sulfur atom, a selenium atom or NR23 among which oxygen, sulfur and NR23 are preferred. In particular, sulfur or oxygen is preferred and further sulfur is most preferred.
As the alkyl, aryl or heterocyclic ring group represented by R21, R22 and R23, those described as R of the methine dyes represented by formula (I) can be exemplified. R21 and R22 preferably are an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl group, sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups. More preferably, either of R21 or R22 is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl or 4-sulfobutyl, and the other is carboxymethyl or methanesulfonylcarbamoylmethyl.
Preferable R23 is an unsubstituted alkyl group, and particularly preferably methyl and ethyl.
The substituents represented by V21, V22, V23 and V24 are those defined as V described above, but two adjacent substituents are not condensed together to form a saturated or unsaturated ring. V21 and V24 are preferably hydrogen atoms, V22 and V23 each is preferably chosen from a hydrogen atom, an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic ring such as 1-pyrrolyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, and halogen atoms such as F, Cl, Br or I. V23 more preferably is a hydrogen atom, while more preferable groups for V22 are halogen atoms, among which Cl or Br is particularly preferred.
The methine groups represented by L21, L22 and L23 may be substituted or unsubstituted with the groups represented by V described above.
n2 represents an integer of 0, 1, 2, 3 or 4; in the case of 2 or larger, methine groups are repeated, but they need not be the same. Preferable values of n2 are 0, 1, 2 or 3, and more preferably 0, 1 or 2, but a particularly preferable value is 0 or 1.
Preferably, L21 represetns an unsubstituted methine group. When n2=1, L22 is preferably a methine group substituted by an unsubstituted alkyl group, and L23 is preferably an unsubstituted methine group. Particularly, L22 is preferably a methine group substituted by a methyl or an ethyl group.
M2 is substantially equivalent to M of the methine dyes represented by formula (I), and preferably a cationic ion. Preferable cations include Na+, K+, triethylammonium, pyridinium and N-ethylpyridinium.
m2 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m2 is 0. A preferred range of m2 is 0, 1, 2 or 3.
Now, the cyanine dyes represented by formula (II) to be used preferably together with the methine dyes represented by formula (I) will be described in detail.
The nitrogen-containing heterocyclic rings represented by Z31 and Z32 may be condensed with a carbocyclic ring such as benzene, cyclohexene or naphthalene, but not with heterocyclic ring.
The ring represented as Z31 or Z32 is preferably thiazoline, thiazole, benzothiazole, oxazoline, oxasole, benzoxazole, selenazoline, selenazole, benzoselenazole, tellurazoline, tellurazole, benzotellurazole, 3,3-dialkylindolenine such as, 3,3-dimethylindolenine, imidazoline, imidazole, benzimidazole, isooxazole, isothiazole, pyrazole, 2-pyridine, 4-pyridine, 2-quinoline, 4-quinoline, 1-isoquinoline, 3-isoquinoline, imidazo[4,5-b]quinoxaline, oxadiazole, thiadiazole, tetrazole, pyrimidine or those obtained by the condensation of a carbocyclic ring such as benzene or naphthalene ring to the rings described above.
More preferably, the nitrogen-containing heterocyclic ring is benzoxazole, benzothiazole, benzimidazole or quinoline, and most preferably, benzoxazole or benzothiazole, which may be substituted with a substituent represented by V described above. Concrete examples are those described as examples for Z11, Z12, Z13, Z14 and Z16 shown in the 23rd to 24th columns of U.S. Pat. No. 5,340,694.
As the alkyl, aryl or heterocyclic ring group represented by R31 and R32, those described as R of the methine dyes represented by formula (I) may be exemplified. R31 and R32 preferably are an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl or sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups. More preferably, either of R31 or R32 is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl or 4-sulfobutyl, and the other is carboxymethyl or methanesulfonylcarbamoylmethyl.
The methine groups represented by L31, L32, L33, L34, L35, L36 and L37 may be unsubstituted or substituted with the groups represented by V described above.
Preferably, L31, L32, L37 and L37 are unsubstituted methine groups.
n3 represents an integer of 0, 1, 2, 3 or 4; for the case of 2 or larger, methine groups are repeated, but they need not be the same. Preferable values of n3 are 0, 1, 2 or 3, and more preferably 0, 1 or 2, and a particularly preferably is 0 or 1.
P31 and P32 each is 0 or 1, preferably 0.
M3 is substantially equivalent to M of the methine dyes represented by formula (I), and preferably a cationic ion. Preferable cations include Na+, K+, triethylammonium, pyridinium and N-ethylpyridinium.
m3 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m3 is 0. A preferred range of m3 is 0, 1, 2 or 3.
The methine dyes represented by formula (II) preferably are further represented by formula (IIa).
In formula (IIa), X41 and X42 each represents an oxygen atom, a sulfur atom, a selenium atom or NR23 among which oxygen, sulfur and NR23 are preferred. In particular, sulfur or oxygen is the most preferred.
As the alkyl, aryl or heterocyclic ring group represented by R41, R42 and R43, those described as R of the methine dyes represented by formula (I) can be exemplified. R41 and R42 preferably are an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl or sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups. More preferably, either of R41 or R42 is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl or 4-sulfobutyl, and the other is carboxymethyl or methanesulfonylcarbamoylmethyl.
Preferable R43 is an unsubstituted alkyl group, and particularly preferably methyl and ethyl.
The substituents represented by V41, V42, V43, V44, V45, V46, V47, and V48 are those defined as V described above, and two adjacent substituents may link together to form a saturated or unsaturated carbocyclic ring. Such saturated or unsaturated carbocyclic rings include, for example, benzene, cyclohexene or naphthalene, and preferably ones which are not condensed.
V41, V44, V45 and V48 are preferably hydrogen atoms, and V42, V43, V46 and V47 each is preferably chosen from a hydrogen atom, an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic ring such as 1-pyrrolyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, and halogen atoms such as F, Cl, Br or I. More preferably, V43 and V47 are hydrogen atoms while more preferable groups for V42 and V46 are halogen atoms, among which Cl or Br is particularly preferred.
The methine groups represented by L41, L42 and L43 may be substituted or unsubstituted with the groups represented by V described above.
n4 represents an integer of 0, 1, 2, 3 or 4; in the case of 2 or larger, methine groups are repeated, but they need not be the same. Preferable values of n4 are 0, 1, 2 or 3, more preferably 0, 1 or 2, and particularly preferably 0 or 1.
M4 is substantially equivalent to M of the methine dyes represented by formula (I), and preferably a cationic ion. Preferable cations include Na30, K30, triethylammonium, pyridinium and N-ethylpyridiniuin.
m4 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m2 is 0. A preferred range of m4 is 0, 1, 2 or 3.
The methine dyes represented by formula (IIa) preferably are further represented by formula (III) when used in green to red sensitive emulsions , and by formula (IV) when used in blue sensitive emulsions.
Next, the dyes represented by formula (III) will be described in detail.
X51 and X52 in formula (III) each represents an oxygen or a sulfur atom. When the dye is used in green sensitive emulsions , X51 is preferably an oxygen or a sulfur atom and X52 an oxygen atom; when the dye is used in red sensitive emulsions X51 is preferably an oxygen or a sulfur atom and X52 is a sulfur atom.
As the alkyl, aryl or heterocyclic ring group represented by R51, R54 and R53, those described as R of the methine dyes represented by formula (I) can be exemplified. R51 and R52 are preferably an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl or sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups More preferably, either of R51 or R52 is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl or 4-sulfobutyl, and the other is carboxymethyl or methanesulfonylcarbamoylmethyl.
Preferable R53 is an unsubstituted alkyl group, and particularly preferably methyl and ethyl.
The substituents represented by V51, V52, V53 V54, V55 and V56 are those defined as V described above, and two adjacent substituents are not linked together to form a saturated or unsaturated ring. V51, V53, V54 and V56 are preferably hydrogen atoms, and V52 and V55 each is preferably an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic ring such as 1-pyrrolyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. More preferable groups for V52 and V55 are halogen atoms, among which Cl or Br is particularly preferred.
M5 is substantially equivalent to the ions represented by M in the methine dyes represented by formula (I), and preferably cationic. Preferable cations include Na+, K+, triethylammonium, pyridinium and N-ethylpyridinium.
m5 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m5 is 0. A preferred range of m5 is 0, 1, 2 or 3.
A detailed description on the dyes represented by formula (IV) will be described below.
In formula (IV), X61 represents an oxygen or a sulfur atom, and particularly preferably sulfur.
As the alkyl, aryl or heterocyclic ring group represented by R61 and R62, those defined as R of the methine dyes represented by formula (I) can be exemplified. R61 and R62 are preferably an alkyl group having a substituent with an acid group or a group with a dissociable proton. Most preferably, substituted alkyl groups contain any one of carboxyl or sulfo group, xe2x80x94CONHSO2xe2x80x94, xe2x80x94SO2NHSO2xe2x80x94, xe2x80x94CONHCOxe2x80x94 or xe2x80x94SO2NHCOxe2x80x94. And particularly preferable groups are 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, carboxymethyl and methanesulfonylcarbamoylmethyl groups. More preferably, either of R61 or R62 is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl or 4-sulfobutyl, and the other is carboxymethyl or methanesulfonylcarbamoylmethyl.
The substituents represented by V61, V62, V63, V64, V65 and V66 are those defined as V described above, but two adjacent substituents do not link together to form a saturated or unsaturated ring. V61, V63, V64 and V66 are preferably hydrogen atoms, V62 and V65 each is preferably an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic ring such as 1-pyrrolyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group or halogen atoms such as F, Cl, Br or I. Among these, halogen atoms are more preferred, and Cl or Br is particularly preferred.
M6 is substantially equivalent to M of the methine dyes represented by formula (I), and preferably a cationic ion. Preferable cations include Na+, K+, triethylammonium, pyridinium and N-ethylpyridinium.
m6 represents an integer of 0 or 1 or more necessary to neutralize the molecular charge, thus in the case where internal salts are formed, m6 is 0. A preferred range of m6 is 0, 1, 2 or 3.
Preferable combinations of the compound represented by formula (I) with the one by formula (II) in the silver halide emulsions of the present invention will be described.
In the case where the emulsion is red sensitive, the compound of formula (II) is further represented by formula (III). In formula (III), both of X51 and X52 are sulfur atoms, each of R51 and R52 is a sulfoalkyl, a carboxyalkyl or an alkylsulfonylcarbamoylalkyl group, R53 is methyl or ethyl, V51, V53, V54 and V56 are hydrogen atoms, V52 and V55 each is preferably an alkyl group such as methyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, and halogen atoms such as F, Cl, Br or I. Among these, halogen atoms are more preferred, and Cl is particularly preferred. M5 represents an organic or inorganic monovalent cation, and m5 is preferably 0 or 1.
The compound of formula (I) to be combined is represented by formula (Ib); either of X21 or X22 is an oxygen atom, the other is a sulfur atom, Y21 is a pyrrole, furan or thiophene ring substituted with halogen atoms, R21 and R22 each is a sulfoalkyl, carboxyalkyl or alkylfulsonylcarbamoylalkyl group, n2 is 1, L21 and L23 are unsubstituted methine groups, L22 is a methyl- or ethyl-substituted methine group, V21, V23 and V24 are hydrogen atoms, and V22 is preferably an alkyl group such as methyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. As V22, halogen atoms are more preferred. M2 is an organic or inorganic monovalent cation, and m2 is preferably 0 or 1.
In the case of green sensitive emulsions, the compound of formula (II) is further represented by formula (III). In formula (III), both of X51 and X52 are oxygen atoms, R51 and R52 each is a sulfoalkyl, a carboxyalkyl or an alkylsulfonylcarbamoylalkyl group, R53 is methyl or ethyl, V51, V53, V54 and V56 are hydrogen atoms, V52 and V55 each is preferably an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic group such as 2-thienyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. Among these, halogen atoms are more preferred. M5 represents an organic or inorganic monovalent cation, and m5 is preferably 0 or 1.
The compound of formula (I) to be combined with the compound described above is represented by formula (Ib); both of X21 and X22 are oxygen atoms, y is a pyrrole, furan or thiophene ring substituted with Cl or Br, R21 and R22 each is a sulfoalkyl, carboxyalkyl or alkylfulsonylcarbamoylalkyl group, n2 is 1, L21 and L23 are unsubstituted methine groups, L22 is a methyl- or ethyl-substituted methine group, V21, V23 and V24 are hydrogen atoms, V22 is an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic group such as 2-thienyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. As V22, halogen atoms are more preferred. M2 is an organic or inorganic monovalent cation, and m2 is preferably 0 or 1.
In the case of blue sensitive emulsions, the compound of formula (II) is further represented by formula (IV). In formula (IV), X61 is a sulfur atom, each of R61 and R62 is a sulfoalkyl, a carboxyalkyl or an alkylsulfonylcarbamoylalkyl group, V61, V63, V64 and V66 are hydrogen atoms, V62 and V65 each is preferably an alkyl group such as methyl, an aryl group such as phenyl, an aromatic heterocyclic group such as 1-pyrrolyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. Among these, halogen atoms are more preferred, Cl being most preferred. M2 represents an organic or inorganic monovalent cation, and m2 is preferably 0 or 1.
The compound of formula (I) to be used with the compound above is represented by formula (Ib); X21 and X22 are sulfur atoms, Y21 is a thiophene ring substituted with halogen atoms, R21 and R22 each is a sulfoalkyl, carboxyalkyl or alkylfulsonylcarbamoylalkyl group, n2 is 0, L21 is a unsubstituted methine group, V21, V23 and V24 are hydrogen atoms, V22 is an alkyl group such as methyl, an alkoxy group such as methoxy, an alkylthio group such as methylthio, cyano group, or halogen atoms such as F, Cl, Br or I. As V22, halogen atoms, in particular Cl and Br, are more preferred. M2 is an organic or inorganic monovalent cation, and m2 is preferably 0 or 1.
The compounds represented by formula (I) of the present invention will be listed not to limit the scope of the present invention to those compounds. The compounds below include those represented by formulae (Ia) and (Ib) which constitute lower concepts of formula (I).
In addition to those described below, the methine dyes S-1 to S-95 described in U.S. patent application Ser. No. 09/536,679 can also be used. 
In the following, the compounds represented by formula (II) of the present invention will be listed not to limit the scope of the present invention to those compounds. The compounds below include those represented by formulae (IIa), (III) and (IV) which constitute lower concepts of formula (II). 
These compounds which are represented by formulae (I) and (II) including those belonging to the lower concepts can be synthesized by the methods described in the following literatures; F. M. Hamer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Cyanine Dyes and Related Compoundsxe2x80x9d, published by John Wiley and Sons (New York, London, 1964), p. 482 to 515, Section 14 in Chapter 18 of D. M. Sturmer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Special Topics in Heterocyclic Chemistryxe2x80x9d published by John Wiley and Sons (New York, London, 1977), and p. 369 to 422, Chapter 15 of Vol. IV part B of xe2x80x9cRodd""s Chemistry of Carbon Compoundsxe2x80x9d, 2nd edition, published by Elsevier Science Publishing Company Inc. (New York).
When the compound represented by formula (I) and the compound represented by formula (II) are used in combination, one compound may be used alone, or two or more kinds of the compounds may be used, in the same emulsion.
The ratio of the compounds of formula (I) to the compounds of formula (II) added to the same emulsion is not specifically limited and depends on the application or the purpose of usage. A preferable range of the ratio is from 1000/1 to 1/1000, more preferably from 100/1 to 1/100, and most preferably from 10/1 to 1/10.
The compounds represented by formula (I) and those by formula (II) can be used in an emulsion in combination with other sensitizing dyes. Examples of such additional dyes preferably include cyanines, merocyanines, rhodacyanines, trinuclear and tetranuclear merocyanines, allopolar dyes, hemicyanines and styryl dyes. More preferable dyes are cyanines, merocyanines and rhodacyanines, among which cyanine dyes are particularly preferred. Detailed descriptions on these dyes are found in F. M. Hamer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Cyanine Dyes and Related Compoundsxe2x80x9d, published by John Wiley and Sons (New York, London, 1964), p. 482 to 515, and Section 14 in Chapter 18 of D. M. Sturmer, xe2x80x9cHeterocyclic Compoundsxe2x80x94Special Topics in Heterocyclic Chemistryxe2x80x9d, published by John Wiley and Sons (New York, London, 1977).
Formulae for preferable additional dyes are found in p. 32 to 44, U.S. Pat. No. 5,994,051, and p. 30 to 39, U.S. Pat. No. 5,747,236 in which some concrete examples are also shown.
Formulae for preferable cyanine, merocyanine and rhodacyanine dyes include (XI), (XII) and (XII) shown in the 21st to 22nd columns of U.S. Pat. No. 5,340,694, in which, however, the integers for n12, n15, n17 and n18 are not limited, being 0 or more (preferably 0 to 4).
One or more kinds of such additional dyes may be used; when two or more kinds are used, combinations exerting a supersensitizing effect are preferred. Typical examples are described in U.S. Pat. Nos. 2,688,545, 2,977,229, 3,397,060, 3,522,052, 3,527,641, 3,617,293, 3,628,964, 3,666,480, 3,672,898, 3,679,428, 3,303,377, 3,769,301, 3,814,609, 3,837,862 and 4,026,707, British Patent Nos. 1,344,281 and 1,507,803, JP-B-43-49336 and JP-B-53-12375 (The term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) JP-A-52-110618 and JP-A-52-109925.
The emulsion of the present invention may contain dyes having no spectral sensitizing effect itself or those that absorb substantially no visible light but exhibit supersensitizing effect.
Useful supersensitizers for the spectral sensitization of the present invention include, for example, pyrimidylamino compounds, triazinylamono compounds, azolium compounds, aminostyryl compounds, aromatic organic acid-formaldehyde condensates, azaindene compounds and cadmium salts. Preferable combinations of supersensitizers and sensitizing dyes are described in, for example, U.S. Pat. Nos. 3,511,664, 3,615,613, 3,615,632, 3,615,641, 4,596,767, 4,945,038, 4,965,182, 2,933,390, 3,635,721, 3,743,510, 3,617,295 and 3,635,721. Preferable methods of using such compounds are also described in the patents listed above.
Detailed descriptions on silver halide photographic emulsions and materials of the present invention will be described.
The methine dyes represented by formulae (I) and (II) (and other sensitizing dyes as well as supersensitizers) may be added to the silver halide emulsion at any emulsion preparation step that is recognized as useful in the art. For example, as is described in U.S. Pat. Nos. 2,735,766, 3,628,960, 4,183,756 and 4,225,666, JP-A-58-184142 and JP-A-60-196749, the dyes may be added during silver halide grain forming step and/or prior to desalting step, during desalting step and/or in the period between desalting and the initiation of chemical ripening. Further, as is described in JP-A-58-113920, the dyes may be added immediately before and during chemical ripening, at any point in time after chemical ripening until coating. Further, as is described in U.S. Pat. No. 4,225,666 and JP-A-58-7629, one compound may be added solely or in combination with another compound of a foreign structure during grain forming step, during and after chemical ripening step, or before, during or after chemical ripening in divided amounts. In such divided additions, combinations of compounds may be altered for each addition.
The added amount of the methine dye (and other sensitizing dyes as well as supersensitizers) used in the present invention which depends on the shape and size of silver halide grains, is from 1xc3x9710xe2x88x926 to 8xc3x9710xe2x88x923 mole per mole silver halide. For example, in the case of silver halide grains of 0.2 to 1.3 xcexcm in size, a preferable addition amount is 2xc3x9710xe2x88x926 to 3.5xc3x9710xe2x88x923 mole and a more preferable one is 7.5xc3x9710xe2x88x926 to 1.5xc3x9710xe2x88x923 mole per mole silver halide.
The methine dye (and other sensitizing dyes as well as supersensitizers) used in the present invention may be dispersed directly in the emulsion, or first may be dissolved in a suitable solvent such as methyl alcohol, ethyl alcohol, methyl cellosolve, acetone, water, pyridine or mixtures of these, and then added to the emulsion in the form of solution. In the dye solution, a base, an acid or a surfactant may be incorporated. And, ultrasonic wave may be used to dissolve dyes. Suitable adding methods for these compounds include one described in U.S. Pat. No. 3,469,987 comprising dissolving a compound to be added in a volatile solvent, dispersing the resulting solution into a hydrophilic colloid, and adding the dispersion to the emulsion, one described in JP-B-46-24185 comprising dispersing the dye to be added in an aqueous solvent, and adding the resulting dispersion to the emulsion, one described in U.S. Pat. No. 3,822,135 comprising dissolving the dye in a surfactant, and adding the resulting solution to the emulsion, one described in JP-A-51-74624 comprising dissolving the dye by using a compound that causes red shift, and adding the resulting solution to the emulsion, and one described in JP-A-50-80826 comprising dissolving the dye in an acid substantially free of water, and adding the resulting solution to the emulsion. Still other methods described in U.S. Pat. Nos. 2,912,343, 3,342,605, 2,996,287 and 3,249,835 can also be used.
Organic solvents used to dissolve the methine dyes of the present invention include, for example, methyl alcohol, ethyl alcohol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, benzyl alcohol, fluorinated alcohols, methyl cellosolve, acetone, pyridine and mixtures of these compounds.
To dissolve the methine dye of the present invention, a base material is preferably added to the solvent system comprising water, organic solvents described above or mixed solvent thereof. Suitable base materials may be an organic or inorganic salt. For example, amine derivatives such as triethylamine or triethanolamine, pyridine derivatives, sodium hydroxide, potassium hydroxide, sodium acetate and potassium acetate can preferably used. A preferable dissolving method comprises adding the dye in the mixed solvent comprising water and methanol, and then adding triethylamine in an molar amount equal to that of the dye.
The silver halide emulsion used in the present invention can contain silver halide grains comprising silver chloride, silver bromide, silver chlorobromide, silver iodobromide, silver iodochloride or silver chloroiodobromide. When the emulsion is used for color photographic paper, silver chlorobromide emulsions are preferred from the viewpoint of rapid and simple processing. Such high chloride content silver halide emulsions which consist of silver chloride, chlorobromide or chloroiodobromide grains is preferably contain not less than 80 mole % of silver chloride. When the emulsion is used for color picture-taking negative or reversal films, silver iodobromide emulsions are preferred. Such emulsions which consist of silver bromide, iodobromide or chloroiodobromide grains preferably contain not less than 95 mole % of silver bromide.
The mean grain size of the silver halide grains contained in the silver halide emulsion of the present invention represented by the number-averaged grain size calculated from the circle having the same projection area as the actual grain is preferably from 0.1 to 2 xcexcm.
Further, the coefficient of variation (the standard deviation of the grain size distribution divided by the mean grain size) of the grain size is 20% or less, preferably 15% or less, and more preferably 10% or less corresponding to mono-disperse emulsion. To secure wide exposure latitudes, a plurality of such mono-disperse emulsions may be blended or coated as multi-layers.
The preferable shape of the silver halide grains contained in the photographic emulsion of the present invention includes regular ones such as cubic, octahedral or tetradecahedral, irregular or ones such as spherical, tabular or mixtures of these. In the present invention, the emulsion preferably contains regular shaped grains in an amount of 50% or more, preferably 70% or more and more preferably 90% or more.
The emulsion used in the present invention can be prepared by the methods described in P. Glafkides, xe2x80x9cChimie et Phisique Photographiquexe2x80x9d, published by Paul Montel Co., in 1967, G. F. Duffin, xe2x80x9cPhotographic Emulsion Chemistryxe2x80x9d, published by Focal Press in 1966, and V. L. Zelikman et al, xe2x80x9cMaking and Coating Photographic Emulsionxe2x80x9d, published by Focal Press in 1964. In other words, any of acid, neutral and ammonia processes maybe used; as the method of reacting a water-soluble silver salt with a water-soluble halide, single jet method, double jet method and the combination of these methods may be used. Further, the so-called xe2x80x9creverse mixing methodxe2x80x9d, in which grains are formed under the presence of excessive silver ion, may also be used. The so-called xe2x80x9ccontrolled double jet methodxe2x80x9d may be used, too, in which, as a modified mode of simultaneous addition method, the pAg of the liquid phase in which silver halide grains are formed is kept constant. According to the controlled double jet method, grains tend to assume regular crystalline shapes and have a narrow size distribution, thus giving rise to mono-disperse emulsions.
In the emulsion used in the present invention, 50% or more, preferably 70% or more, and more preferably 80% or more of the total projected area of the silver halide grains is preferably tabular grains with an aspect ratio of 2 or more, preferably 4 to 100, more preferably 6 to 80 and particularly preferably 8 to 60. When the emulsion is applied to color photographic paper, silver chlorobromide tabular grains are suited while for color picture-taking films, silver iodobromide tabular grains are suited.
In general, a tabular grain has two parallel planes, and the thickness of the tabular grain means the distance between these two parallel planes. On the other hand, the diameter of a silver halide grain is defined as the diameter of a circle having the same area as the projection area of the grain recorded in electron microscope photographs. The aspect ratio of a tabular grain is defined by the ratio of the diameter to the thickness.
Tabular silver halide grains used for color photographic paper are preferably high chloride content silver halide grains containing preferably 80% or more, more preferably 95% or more, of silver chloride.
The high chloride content silver halide grains used in the present invention comprise a core and a shell (an outermost layer) containing a larger amount of iodide than the core. It is desirable that the core contains not less than 90% of silver chloride. The core may consist of two or more parts different in halide composition. The volume of the shell is preferably 50% or less and more preferably 20% or less of the total grain volume. The silver iodide content of the shell is preferably 0.5 to 13 mole % and more preferably 1 to 6 mole %. The silver iodide content in the total grain is preferably 0.1 to 5 mole % and more preferably 0.1 to 2 mole %.
The silver iodide content of the core is preferably 1 mole % or less, and particularly preferably 0 mole %.
The silver bromide content, which may differ between the core and the shell, is preferably 0 to 20 mole % and more preferably 0.1 to 5 mole % based on the total silver amount.
The diameter of the tabular silver halide grain used in the present invention is preferably 0.2 to 1.0 xcexcm. The term xe2x80x9cdiameterxe2x80x9d of a silver halide grain is defined as that of a circle having the same area as the projection area of the grain recorded by electron microscope photograph. On the other hand, the grain thickness is preferably 0.2 xcexcm or less, more preferably 0.15 xcexcm or less and most preferably 0.1 xcexcm or less. The aspect ratio of a tabular grain (defined by the ratio of the diameter to the thickness) is preferably not less than 2, and more preferably 3 to 20.
In general, a tabular grain has two parallel planes, and the thickness of the tabular grain means the distance between these two parallel planes.
Though the size distribution of the silver halide grain used in the present invention may be poly- or mono-dispersed, mono-dispersed ones are preferred. The coefficient of variation for grain size is 5 to 25%, and in particular 5 to 20%.
The coefficient of variation for grain thickness is preferably 5 to 25% and in particularly preferably 5 to 15%.
Now, the preparation of {111} tabular grain will be described.
High chloride content silver halide tabular grains having {111} faces as their main outer surfaces can be formed by using the crystal habit controlling agent. Further, tabular grains can be formed by generating two parallel twin planes. As the generation of twin planes depends on the temperature, the dispersant (gelatin) and silver halide concentration, appropriate conditions including these factors must be established. In cases where a crystal habit controlling agent is used in the step of nuclear formation, the gelatin concentration of from 0.1 to 10% is preferred, while the chloride concentration is preferably not lower than 0.01 mole/L, and more preferably not lower than 0.03 mole/L.
To achieve a mono-dispersion, it is desirable not to use crystal habit controlling agents at the step of nuclear formation as is described in JP-A-8-184931. When crystal habit controlling agents are not used at the nuclear formation step, the concentration of gelatin is preferably 0.03 to 10%, and more preferably 0.05 to 1.0%, while the chloride concentration is preferably 0.01 to 1 mole/L, more preferably 0.003 to 1 mole/L. The temperature for nuclear formation is set at 2 to 90xc2x0 C., preferably at 5 to 80xc2x0 C. and particularly preferably at 5 to 40xc2x0 C.
Nuclei for tabular grains are formed during the first nuclear formation step, but in the reaction vessel there are also present many nuclei of grains other than tabular grains. Accordingly, a technique is required with which only tabular nuclei are retained by diminishing all the other types of nuclei during ripening. When the ordinary Ostwald ripening is performed, tabular nuclei also tend to dissolve away, leading an undesirable size increase of tabular grains obtained by the decrease in the number of tabular nuclei. To prevent such adverse result, crystal habit controlling agents are used. Particularly, by jointly using phthalated or trimellited gelatin, the effect of crystal habit controlling agents is enhanced and the solution of tabular nuclei is prevented.
The value of pAg during ripening, which plays a specifically important role, is 60 to 130 mV relative to the silver/silver chloride electrode.
As a next step, tabular nuclei thus prepared are subjected to crystal growth via physical ripening and with the addition of silver salts and halides under the presence of crystal habit controlling agents. During crystal growth, the chloride concentration is preferably 5 mole/L or less, and more preferably 0.05 to 1.0 mole/L. The temperature during crystal growth, which is 10 to 90xc2x0 C. and preferably 30 to 80xc2x0 C. The total amount of the crystal habit controlling agent is preferably 6xc3x9710xe2x88x925 or more and more preferably 3xc3x9710xe2x88x924 to 6xc3x9710xe2x88x922 mole, per mole of silver halide in the finished emulsion. The crystal habit controlling agent may be added at any time of from the steps of nuclear formation to the step of physical ripening or crystal growth of silver halide grains. When the crystal habit controlling agent is added, the formation of {111} faces starts. The crystal habit controlling agent may be present in the reaction vessel prior to nuclear formation, however in order to produce tabular grains of small sizes, it is desirable to add the agent stepwise to the reaction vessel along with grain growth to gradually increase the concentration of the agent.
In cases where the quantity of dispersing medium needed for nuclear formation is too small for grain growth, the medium must be replenished. Usually, grain growth needs the presence of 10 to 100 g/L gelatin. Among various types of gelatin, phthalated or trimellitated one is preferred.
The pH value during grain formation is arbitrary, but neutral to acidic regions are preferred.
As the presence of the crystal habit controlling agent after the completion of grain formation has influences on the adsorption of sensitizing dyes and on the behavior during development, the crystal habit controlling agent is preferably eliminated after grain formation. It is noted, however, that high chloride content silver halide grains hardly keep the {111} faces in the absence of crystal habit controlling agents under ordinary conditions. Hence, it is preferred that the grain form is maintained by replacing the agent with certain photographically useful compounds such as sensitizing dyes. Such replacing methods are disclosed in JP-A-9-80656 and JP-A-9-106026, U.S. Pat. Nos. 5,221,602, 5,286,452, 5,298,387, 5,298,388 and 5,176,992.
By any of the replacing operations described above, crystal habit controlling agents are desorbed from the grain surface, and it is preferred to remove the desorbed agent from the emulsion by washing with water. Such washing can be performed at temperatures not causing the gelation of gelatin. Examples of suitable washing methods include those well known in the art such as those based on flocculation and ultrafiltration. For pyridinium salts as crystal habit controlling agent, washing is carried out at a temperature of preferably not lower than 40xc2x0 C., and more preferably not lower than 50xc2x0 C. As the flocculant used for flocculation washing, compounds having a sulfonic acid group or a carboxylic acid group are used. Pyridinium salts as crystal habit controlling agent tend to form salts with flucculants having sulfonic acid groups due to their strong interactions with sulfonic acid groups. Such salt formation makes the elimination of the pyridinium salt from the emulsion difficult. Accordingly, flocculants having carboxylic acid groups are preferred. Concrete examples of flucculants having carboxylic acid groups are described in British Patent No. 648,472.
As the desorption of crystal habit controlling agents are promoted under low pH conditions, it is preferred that the pH of washing water is lower unless the grain aggregation does not cause.
Preferable crystal habit controlling agents are preferably chosen from the compounds represented by formulae (A), (B) and (C). 
In the formula, R1 represents an alkyl group, an alkenyl group or an aralkylo group, and R2, R3, R4, R5 and R6 each represents a hydrogen atom or a substituent. R2 and R3, R3 and R4, R4 and R5, and R5 and R6 may be condensed together to form a ring, provided that, at least one of R2, R3, R4, R5 and R6 represents an aryl group, and Xxe2x88x92 represents a counter anion. 
In the formulae, A1, A2, A3 and A4 each represents a group of non-metallic atoms necessary to form a nitrogen-containing heterocyclic ring, and may be the same or different from each other. B represents a bivalent linking group, and m represents an integer of o or 1. R1 and R2 each represents an alkyl group, and X represents an anion. n11 represents an integer of 0 or 1. When an intramolecular salt is formed, n11 is 0.
Now, the compounds represented by formula (A) will be described in detail.
In formula (A), R1 represents a straight, branched or cyclic chain alkyl group such as methyl, ethyl, isopropyl, t-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl or cyclohexyl, a C2-20 alkenyl group such as allyl, 2-butenyl or 3-pentenyl, a C7-20 aralkyl group such as benzyl or phenethyl. These groups represented by R1 may be substituted with those represented by the following R2 to R6.
R2, R3, R4, R5 and R6 may be the same or different, representing a hydrogen atom or groups that are replaceable with the hydrogen. Examples of the atoms or groups include the following ones.
Halogen atoms, alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, aryl groups, heterocyclic rings such as pyridyl, furyl, imidazolyl, pyperidinyl or morpholino, alkoxy groups, aryloxy groups, amino groups, acylamino groups, ureido group, urethane group, sulfonylamino group, sulfamoyl group, carbamoyl group, sulfonyl group, sulfinyl group, alkyloxycarbonyl groups, acyl group, acyloxy group, phosphoric acid amide group, alkylthio groups, arylthio groups, cyano group, sulfo group, carboxy group, hydroxy group, phosphono group, nitro group, sulfino group, ammonium groups such as trimethylammonium, phosphonium groups and hydrazino group. These groups may be further substituted.
Each pair of R2 and R3, R3 and R4, R4 and R5, and R5 and R6 may be linked together to form a quinoline ring, an isoquinoline ring or an acridine ring.
Xxe2x88x92 represents a counter anion such as halogen (Clxe2x88x92 or Brxe2x88x92) nitrate, sulfate, p-toluenesulfonate or trifluoromethanesulfonate ion.
In formula (A), preferably, R1 represents an aralkyl group, and at least one of R2, R3, R4, R5 and R6 represents an aryl group.
More preferably, R1 of formula (A) represents an aralkyl group, R4 represents an aryl group, and Xxe2x88x92 represents a halogen ion. Some examples of such compounds are described in EP 723187A as crystal habit controlling agents 1 to 29. However, the scope of the present invention is not be limited by such examples.
Detailed descriptions on the compounds represented by formulae (B) and (C) of the present invention will described below.
A1, A2, A3 and A4 each represents a group of non-metallic atoms necessary to form a nitrogen-containing heterocyclic ring that may contain oxygen, nitrogen or sulfur atom and be condensed with a benzene ring The heterocyclic ring formed by each of A1, A2, A3 and A4 may be substituted, and may be the same or different each other. Examples of preferable substituents include alkyl groups, aryl groups, aralkyl groups, alkenyl groups, halogen atoms, acyl groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, sulfo group, carboxy group, hydroxy group, alkoxy groups, aryloxy groups, amide groups, sulfamoyl group, carbamoyl group, ureido group, amino groups, sulfonyl group, cyano group, nitro group, mercapto group, alkylthio groups and arylthio groups. As a preferable combination, A1, A2, A3 and A4 each is chosen from a 5- or 6-membered ring such as pyridine, imidazole, thiazole, oxazole, pyradine or pyrimidine. Among these rings, pyridine is most preferred. B represents a divalent linking group such as alkylene, arylene, alkenylene, xe2x80x94SO2xe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94 and xe2x80x94N(R2)xe2x80x94, in which R2 is an alkyl group, an aryl group or a hydrogen atom. Preferable examples for B are alkylene and alkenylene.
R1 and R2 each represents an alkyl group having 1 to 20 carbon atoms. R1 may be the same as or different from R2.
The alkyl group here represents substituted or unsubstituted ones, in which the substituents represents those for A1, A2, A3 and A4.
As preferable examples, R1 and R2 are alkyl groups having 4 to 10 carbon atoms. As most preferable examples, R1 and R2 each is an alkyl group substituted with unsubstituted or substituted aryl groups. X represents an anion such as Clxe2x88x92, Brxe2x88x92, Ixe2x88x92, nitrate, sulfate, p-toluenesulfonate or oxalate ion. n represents 0 or 1; in intramolecular salts, n is 0.
Concrete examples of the compound represented by formula (B) or (C) are disclosed in JP-A-2-32 as exemplary compounds 1 to 42. It is self-evident that the scope of the present invention is no limited to those compounds.
Now, {100} tabular grains will be explained.
This type of grain has {100} faces as its main planes. The shapes of the main plane include rectangular parallelogram, three- to five-cornered shapes obtained by lacking in one right triangle forming a corner of the rectangular parallelogram, and four- to eight-cornered shapes obtained by lacking in two to four right triangles forming corners of the rectangular parallelogram. To make sure, the lacking part is a right triangle which is formed by the two sides forming a corner of the rectangular parallelogram and has the corner as its vertex.
A supplemented quadrilateral is defined by supplementing the lacking parts to restore the initial rectangular parallelogram. Then, the ratio of the adjacent sides of such parallelogram and quadrilateral (the longer side length divided by the shorter side length) is 1 to 6, preferably 1 to 4 and more preferably 1 to 2.
Tabular silver halide grains having {100 }main planes can be prepared by mixing, in a dispersing medium such as aqueous gelain, an aqueous silver salt solution with an aqueous halide salt solution under stirring. Among such preparing methods, JP-A-6-301129, JP-A-6-347929, JP-A-6-34045 and JP-A-9-96881 disclose use of silver iodide or iodide ion, or silver bromide or bromide ion in order to introduce distortions in the grains owing to the difference in the crystal lattice sizes of silver chloride from those of silver iodide or bromide. The introduction of such distortions leads to crystalline defects such as spiral dislocation that promotes anisotropic crystal growth. Once such spiral dislocation is introduced, the formation of the two-dimensional nucleus in that plane does not act as rate-determinant factor under low super-saturated conditions. Accordingly, the crystallization in the plane is promoted, and introduced with spiral dislocation and resulting in a tabular grain. Preferable low super-saturated conditions mean 35% or less of critical addition condition, and more preferably 2 to 20% of the critical condition. It must be noted that the crystalline defect playing the key role has not been identified as spiral dislocation, however, the direction of the introduced dislocation or the fact that an anisotropic growing property is imparted to the grain strongly suggests that the defect be a spiral dislocation. In order to make tabular grains thinner, it is desirable, as disclosed in JP-A-8-122954 and JP-A-9-189977, to maintain the introduced dislocation.
The mixing condition during nuclear formation is very important. To prepare tabular grains with a narrow distribution of the thickness, a highly efficient mixing is needed to completely mix the silver nitrate solution with the halide solution in a short period. In the case where the mixing device disclosed in JP-A-51-83097 is used, the rotation of the agitator is preferably adjusted to 800 to 2000 rpm and more preferably 1000 to 2000 rpm.
Japanese PP-A-6-347928 discloses the use of imidazoles or 3,5-diaminotriazole while JP-A-8-339044 describes the use of poly(vinyl alcohol). The two patents aim to prepare {100} tabular grains by adding the compounds described above as promoters for {100} face formation. Though the present invention can make use of these methods, the scope of the present invention is not limited to them
Silver halide tabular grains used for picture-taking color films comprises silver iodobromide, silver iodochloride or silver iodochlorobromide, all containing silver iodide of not larger than 30 mole %. Particularly preferably compositions are silver iodobromide or silver iodochlorobromide containing 2 to 10 mole % of silver iodide. They may contain silver chloride, but the silver chloride content is preferably 8 mole % or less, more preferably 3 mol % or less, and most preferably 0 mole %.
The diameter of such silver iodobromide tabular grains preferably is 0.3 to 5.0 xcexcm. On the other hand, the thickness of the tabular grains is preferably 0.05 to 0.5 xcexcm. The aspect ratio preferably is 4 to 50, more preferably 5 to 30, and most preferably 6 to 25.
In the silver halide grains of the present invention, metals belonging to group VIII of Periodic Table, i.e., osmium, iridium, rhodium, platinum, ruthenium, palladium, cobalt, nickel, and iron can be incorporated in the form of ion or complex ion individually or in combination.
Further, these metal may be used with plural kinds.
Any compound that acts as the source of the metal ion described above can be added to the dispersion medium such as an aqueous gelatin solution, an aqueous halide solution or additional aqueous solutions all used for silver halide grain formation. Alternatively, such a compound is firstly incorporated in silver halide fine grains, which are then added to a silver halide emulsion; via various procedures such as dissolving the emulsion, the metal ion is included in the silver halide grains of the present invention. Such metal ion can be introduced into the grains at any point in time, i.e., before, during or immediately after grain formation, and the introduction timing is altered depending on in which place in the grain and how much the metal ion is located.
In the case of high chloride content silver halide grains of the present invention, not less than 50 mole %, preferably not less than 80 mole % and more preferably 100 mole % of the total metal ion source compound is localized in the surface portion of the grains corresponding to 50 volume % or less of the total grain volume. More preferably, the source compound is localized in the superficial portion of the grains having 30 volume % or less of the total grain volume. By localizing the metal ion near the grain surface, the internal sensitivity of the grain will not rise, leading to obtain high photographic speeds. To make the metal ion source compound concentrated at the superficial portion of silver halide grains, first only the core of silver halide is formed followed by the formation of the surface portion by reacting an aqueous silver salt solution with an aqueous halide solution in the presence of metal ion source compounds.
Besides metals belonging to group VIII, other polyvalent metal ion impurities can be incorporated into the silver halide emulsion of the present invention at any step from grain formation to physical ripening. Preferable addition amounts of such impurities, which vary depending on their purposes, are between 10xe2x88x929 and 10xe2x88x922 mole per mole silver halide.
The silver halide emulsions used in the present invention are usually chemically sensitized. Suitable chemical sensitization methods include gold sensitization using gold compounds (See, for example, U.S. Pat. Nos. 2,448,060 and 3,320,069.), sensitization using metals such as iridium, platinum, rhodium or palladium (See, for example, U.S. Pat. Nos. 2,448,060, 2,566,245 and 2,566,263.), sulfur sensitization using sulfur compounds (See for example, U.S. Pat. No. 2,222,264), selenium sensitization using selenium compounds, tellurium sensitization using tellurium compounds and reduction sensitization using stannous salts, thiourea dioxide or polyamines (See, for example, U.S. Pat. Nos. 2,487,850, 2,518,698 and 2,521,925.). These methods can be adopted individually or in combination.
The silver halide emulsions used in the present invention are preferably subjected to gold sensitization that can minimize the variation of photographic properties related to scanning exposure with laser and other light sources. For gold sensitization, chloroauric acid or salts thereof, gold thiocyanate and gold thiosulfate can be used. The added amount of such compounds is preferably 5xc3x9710xe2x88x927 to 5xc3x9710xe2x88x922 mole and more preferably 1xc3x9710xe2x88x926 to 1xc3x9710xe2x88x923 mole per mole silver halide. Such compounds for gold sensitization may be added by the end of the chemical sensitization adopted in the present invention.
Other sensitizations including sulfur, selenium, tellurium or reduction sensitization or sensitization with noble metal compounds other than gold compounds can be preferably combined with gold sensitization.
Among those chemical sensitizations, selenium sensitization is particularly preferred for the emulsions used in the present invention.
Various selenium compounds described in a number of published patents can be applied as selenium sensitizer. Concretely, an labile or non-labile selenium compound is added to the emulsion, which is agitated for a pre-determined period at an elevated temperature of 40xc2x0 C. or higher. Labile selenium compounds include, for example, those disclosed in JP-B-44-15748, JP-B-43-13489, JP-A-4-25832 and JP-A-4-109240. Concrete examples of the labile selenium sensitizers include isoselenocyanates (for example aliphatic isoselenocyanate such as allylisoselenocyanate), selenoureas, selenoketones, selenoamides, selenocarboxylic acids (for example, 2-selenopropionic acid and 2-selenolactic acid), selenoesters, diacyl selenides (for example, bis(3-chloro-2,6-dimethoxybenzoyl) selenide), selenophosphates, phosphine selenides and colloidal selenium metal.
The preferable labile selenium compounds described above do not limit the scope of the present invention. As is well understood by emulsion engineers, the chemical structure of labile selenium compounds do not exert any significant influence on the property of the compounds as chemical sensitizer so far as the compounds are chemically labile. In other words, the role of the organic portion of the selenium sensitizer molecule is only to hold and introduce selenium into the emulsion. Therefore, in the present invention a variety of labile selenium compounds that can satisfy the above condition can be advantageously used without limitation.
Stable selenium compounds used in the present invention include those disclosed in JP-B-46-4553, JP-B-52-34492 and JP-B-5234491. Examples of the labile selenium sensitizers are, for example, selenious acid, potassium selenocyanide, selenazoles, quaternary salts of selenazoles, diaryl selenide, diaryl diselenide, dialkyl selenide, dialkyl diselenide, 2-selenazolidine-dione, 2-selenazolidine-thione, and the derivatives of these compounds.
Among such selenium compounds, those represented by formulae (VII) and (VIII) of JP-A-11-15115 are preferably used.
These compounds are dissolved in water, organic solvents such as methanol or ethanol, or in mixed solvents and added during chemical sensitization. They are preferably added prior to chemical sensitization. One or more kinds of selenium sensitizers may be used. Combinations of labile selenium compounds with non-labile selenium compounds are also preferred.
The addition amount of selenium sensitizers, which varies depending on the activity of the sensitizer to be used, the type and size of silver halide grains to be sensitized and ripening temperature and period, is preferably not lower than 1xc3x9710xe2x88x928, and more preferably 1xc3x9710xe2x88x927 to 5xc3x9710xe2x88x925 mole, per mole of silver halide of the emulsion. The temperature for chemical ripening using selenium sensitizer is 45xc2x0 C. or more, and preferably 50 to 80xc2x0 C. The pAg and pH are arbitrary. For example, the advantageous effects of the present invention can be achieved by pH values of from 4 to 9.
The silver halide emulsion used for the present invention can be added with various compounds or their precursors that act to prevent fog or stabilize photographic properties over the period of manufacture and storage and during photographic processing. Concrete examples of such compounds are described in p.39 to p.72 of JP-A-62-215272. Furthermore, 5-arylamino-1,2,3,4-thiatriazole compounds in which the aryl moiety has at least one electron attractive group are also preferably used.
The silver halide emulsions prepared according to the present invention can be used for color and black-and-white photographic materials. Color photographic materials include color photographic print materials, picture-taking negative and color reversal films while black-and-white materials include X-ray films, picture-taking negative films and graphic arts printing films.
Among various types of supports for the color photographic print materials used in the present invention including transparent and reflective ones, reflective supports are preferred. Particularly, those comprising a plurality of water-resistant resin layers such as polyethylene or polyester film layers which are laminated on a base and at least one of which contains a white pigment and/or a colored pigment such as ultramarine are particularly preferred.
Further, such a water-resistant resin layer preferably contain a fluorescent whitening agent. Alternatively, the whitening agent may be dispersed in the hydrophilic colloid layer of the photographic material. Preferable whitening agents include benzoxazole, cumarine and pyrazoline compounds. Particularly preferably fluorescent whitening agents are benzoxazolylnaphthalene and benzoxazolylstylbene compounds. These compounds can be preferably used in an amount of 1 to 100 mg/m2, but there is no special limitation on the amount per unit area. When the whitening agent is mixed in a water-resistant resin, its content is preferably 0.0005 to 3% by weight and more preferably 0.001 to 0.5% by weight, based on resin weight.
Other types of reflective supports applicable to the present invention include the following. Base materials comprising a transparent film such as cellulose triacetate, poly(ethylene terephthalate), polyesters obtained by 2,6-naphthalene dicarboxylic acid (NDCA) and ethylene glycol (EG), or NDCA and terephthalic acid with EG, films coated with a magnetic recording layer, and those comprising a reflective support described above and a hydrophilic pigmented colloid layer containing white and colored pigments provided on such support.
With the purpose of improving image sharpness, the photographic materials of the present invention can be incorporated with a dye (particularly those of oxonol type) that can be decolorized by photographic processing Such dyes that are described in p.27 to p.76 of European Patent EP 0,337,490A2 are used in such an amount that the optical reflection density at 680 nm of the photographic material be at least 0.50.
In the present invention, a colored coating that can be decolorized during processing can be used in combination with or instead of water-soluble dyes. Such a decolorizable colored layer can be arranged in direct contact with the emulsion layer, or adjacent to an intermediate layer containing a color mixing preventing agents such as gelatin or hydroquinone which act to prevent color mixing occurring during processing. Such colored layer is preferably arranged beneath (closer to the support) the emulsion layer that records images of the same primary color as the color of the colored layer. One colored layer may be combined to every primary color image recording emulsion layer, or to limited emulsion layers. Alternatively, such a colored layer may be employed that is colored so as to cope with plural emulsion layers. The optical reflection density of such colored layer is preferably 0.2 to 3.0, more preferably 0.5 to 2.5 and particularly preferably 0.8 to 2.0 at the wavelength of the light source used for scanning exposure or at the one corresponding to the peak adsorption of the layer.
The color photographic print materials (color print paper) maybe not only areal-exposed but also scanning-exposed.
In typical scanning exposure, semiconductor lasers emitting visible light are modulated by image information. When visible light is not emitted from a semiconductor laser, a second harmonic generator (SHG) device comprising nonlinear optical crystals are used in combination with such a laser.
The diameter of the scanning beam, which is usually 150 xcexcm or less, preferably 10 to 120 xcexcm, and more preferably 20 to 100 xcexcm.
The diameter of light beam is defined as that of such a circle in the cross section perpendicular to the beam axis that, at the peripheral of the circle, the light intensity declines to 1/e2 (e being the base of natural logarithms) of the intensity at the beam axis.
The shape of the light beam for scanning exposure is not limited but preferably is substantially circular. The term xe2x80x9csubstantiallyxe2x80x9d used here means that the ratio of the diameter along the sub-scanning direction to that along the main scanning direction is from 97 to 103%.
The effective beam diameter in scanning exposure can be obtained by the method described in the lower left column of p.4, JP-A-5-19423. The method consists of one scanning line exposing using the laser beams outputing an intensity equal to 50% of the laser intensity enough to give the maximum color-forming density of the formed image and then color-developing to obtain the linear color forming image. The density profile of the resulting linear image is obtained by scanning it with a micro-densitometer along the direction perpendicular to the line direction. The effective beam diameter is defined as the line width within which the density is not lower than one fifth of the maximum density Dmax.
The effective diameter at scanning exposure is 300 xcexcm or less, preferably 10 to 240 xcexcm and more preferably 20 to 200 xcexcm.
The scanning pitch in scanning exposure is defined as the raster (beam track) interval, and therefore for a circular light beam, the scanning pitch is equal to the distance between the beam centers. The scanning pitch preferably is narrower than the effective beam diameter. The overlapping width between rasters, L is defined as
L=dxe2x88x92p 
in which p is scanning pitch and d effective beam diameter.
Practically, scanning pitches of 0.25 to 190 xcexcm, and more preferably 2 to 80 xcexcm are used.
The overlapping width, which is not limited but is usually set equal to 5 to 95%, preferably 15 to 85%, and more preferably 20 to 80%, of the effective beam diameter.
Scanning exposure using a light beam can be effected by means of drum scanning, but a method using a polygon mirror rotating at a very high speed is preferred, in which the beam is reflected by the mirror planes to perform main scanning while sub-scanning is carried out by moving the photographic material along the direction perpendicular to the main scanning direction. The number of mirror plane having no special limitation is preferably 2 to 36, and more preferably 6 to 14. A preferable range for stable number of rotation of such polygon mirror is from 4000 to 36000 rpm. By multiplying the number of rotation by the number of mirror plane, the number of scanning lines per minute is obtained.
The exposure time per pixel in scanning exposure is 10xe2x88x924 sec or less, and preferably 10xe2x88x926 sec or less for the pixel density of 400 dpi.
The method of preparing photographic emulsions described in line 36, column 63 to line 2, column 65 of JP-A-10-239789 can be applied to the emulsions used for the present invention.
Further, various additives to emulsions including color coupler, additives for the silver halide photographic materials, the types of photographic materials to which the present invention is applicable and processing methods are described in line 3, column 65 to line 13, column 73 of JP-A-10-239789.
In addition to the various additives described above, still other ones can also be used for the silver halide photographic materials of the present invention depending on the application purposes of the materials.
Such additives are described in detail in Item 17643 (December, 1978), Item 18716 (November, 1979) and Item 308119 (December, 1989) of Research Disclosure Journal. The following table summarizes where each additive is described.
Various technologies such as layer arrangement, silver halide emulsion, functional coupler such as dye forming coupler or DIR coupler, various additives and development treatment all used for the emulsions as well as the photographic materials including such emulsions are described in European Patent No. 0565096A1 (published on Oct. 13, 1993) and the patent specifications described in the above patent. The following table summarizes where each technological term is described.